Otitis media (OM) is the most common illness for which children receive medical care in this country. Approximately $2 billion are spent annually on medical and surgical treatment. On Oct 80, the Otitis Media Research Center was established at the Children's Hospital of Pittsburgh which is focused into five clinical trials and six laboratory/clinical studies in humans and animals. Clinical trials are designed to determine the most effective method of management/prevention of infants and children with acute and recurrent acute OM, and otitis media with effusion (OME). Over 1,800 subjects have entered into the clinical trials. Decongestant and antihistamine (D&A) therapy lacks efficacy for OME, but amoxicillin (without D&A) therapy is effective for OME. Efficacy of other antimicrobial agents (and combinations) is being tested and will continue. Our trials of myringotomy and myringotomy with tympanostomy tube (M&T) for chronic OME indicate that M&T does provide children with less morbidity, but perforation of the tympanic membrane is a complication; final two years treatment/observation needed. Prophylaxis of recurrent acute OM (antimicrobials or M&T) will require further treatment/observation before final outcome is known, and adenoidectomy with and without tonsillectomy (T&A) will require more subjects enrolled and treated/observed to determine outcomes. The trial of antimicrobial therapy/myringotomy for acute OM will be completed as planned. Laboratory/clinical studies include: studies of cross-sectional anatomy and computer imaging of histological and histopathologic specimens of the Eustachian tube (ET) and temporal bone; biochemical and enzyme composition of middle-ear effusions; studies of OME and hearing in a Rhesus monkey animal model; and determine a possible genetic component in OME by comparing the concordance rate and consequences of OME on the auditory pathway in twins prospectively followed from birth. During the next grant years, more knowledge will be gained and information disseminated concerning the etiology, pathogenesis, management and prevention of OM.